Spreadsheet programs and similar programs allow a user to specify data inside cells within various rows and columns. Once the data is entered, users can write formulas that perform calculations against the data in those cells. For example, calculations can be written to add one cell to another in order to generate a total value. Some spreadsheets can grow quite large in size, including hundreds if not thousands of cells of data.
The idea of grouped aggregate views (which are sometimes called pivot tables) was introduced to allow end users to create summary views of a larger set of data in the spreadsheet. Grouped aggregate views will automatically extract, organize, and summarize data from another location, such other sheet(s) in the spreadsheet or another region of the current sheet in the spreadsheet.
While grouped aggregate views are great for summarizing data, one issue that arises is that you cannot easily create calculations directly from within the grouped aggregate view to further refine the summary data being displayed. One issue that arises is that normal spreadsheet calculations cannot easily be applied in these grouped aggregate views. The problem in grouped views is that not all rows are of the same type. For example, some rows might represent totals for particular years, others for states, and others for cities. If a formula that calculates year-over-year growth is desired, the user cannot simply reference the previous row and expect that formula to work throughout the view.